A long fiber composite is different from other composites because the long fiber used for reinforcing the composite has a longer aspect ratio than the one used in other composites. The aspect ratio is the ratio of the width of a fiber to its height.
Generally, the long fiber composite uses a long glass fiber which is impregnated in thermoplastic polymer. The long fiber composite can be prepared by various methods. One of the methods is known as pultrusion.
The long fiber composite prepared by pultrusion has been used for various applications such as automobiles, electrical/electronic devices, computers, and the like.
Japanese 1956-14311 discloses a long glass reinforced resin strand which is prepared by impregnating a melted thermoplastic resin into a bundle of long fibers to impart reinforcement, and by pulling the impregnated long fibers which are twisted by a twist roller, and then, the strand can be cut in order to make pellets.
However, most of the prior art related to pultrusion have problems such as low degree of impregnating of long fiber resulting from a matrix resin having a high viscosity, or low yield resulting from the cutting of yarn.